The first 100 days of a presidency are like the opening chapter of an unfinished novel. It will be possible, by the end, to look back and see the foreshadowing of character traits and plot twists, but for now it is too early to predict what direction the story will take.

You can read the first pages of the Barack Obama opus and construct opposing narratives. The young, naive president, having inherited a full plate, foolishly chooses to pile it higher. Unschooled in the ways of Washington, he arrogantly overestimates his powers of gentle persuasion, undervalues the entrenched forces arrayed against him and, Icarus-like, crashes. This could have been predicted from the opening days, when he signaled weakness by proposing politically difficult steps and then backing down (see: farm subsidies) or misjudging the fallout from actions and words (see: torture commission).

Or, the young president, preternaturally calm and canny beyond his years in Washington, lays out an ambitious agenda with full awareness that he will not obtain all he seeks but knowing that seeds have to be planted before they can grow. He keeps his eyes on the prize -- health-care reform -- without alienating potential allies by dictating carved-in-stone details. Not everything on his to-do list is checked off by the end of his first term, nor did he expect it to be, but the broad outlines of success linger beyond the specific features of failure. Everyone remembers, after all, that George W. Bush got his tax cuts -- not that he failed to achieve his original dollar target.

At this moment, either of these story lines is plausible, which is why the truly hard work of the Obama presidency lies ahead. As difficult as it was to get the stimulus package passed, deciding to spend money is what Congress does most easily, especially if a president mostly lets appropriators have their way. Herding the cats on health care will be much harder, given the competing outside interests and inside demands. Passing a cap-and-trade plan to curb greenhouse gases, given the economic stakes and regional divisions, will make health care look simple.

Getting applause in Europe or South America is easy in the relieved aftermath of the Bush years; the proof will be in the ability to persuade allies to commit troops or money or even display backbone at the United Nations. Reaching out to Cuba or Iran is simple. The trick lies in calibrating the proper course in the aftermath of those overtures, when the outstretched hand is greeted, as it was in the case of Iran, by a slap in the face.

In other words, the first 100 days was the easy part.

When I said this to a senior administration official the other day, I worried that, after 90-plus days of round-the-clock work, and some not insubstantial achievements, he was apt to take my head off.

Instead, he agreed with the point, and he kept returning to it.

Some of the heavy lifting ahead is the result of a deliberate and eminently sensible strategy to push off tough or controversial choices -- kind of like taking an "incomplete" in a college course but knowing that you'll have to write the paper over Christmas break. For instance, the president said he wanted to close Guantanamo; the hard part will be figuring out how to deal with the prisoners remaining there. (Hint of difficulty: France agreed to take one.)

Similarly, the president reaffirmed his promise to end the military's policy of "don't ask, don't tell." But the administration avoided the opening-weeks mess in which the Clinton team found itself by announcing that the reversal, which would require a change in the law, was coming -- but not right now. As Defense Secretary Robert Gates told Fox News Sunday last month, "The president and I feel like we've got a lot on our plates right now and let's push that one down the road a little bit."

At some point, though, the road runs out.

Pick your issue, domestic or foreign: While the first 100 days served to set the stage and dispense with preliminaries, the harder work is ahead. To take a big one, the prospects for major health-care overhaul are as auspicious as they've been in years -- and if the final result reflects a major expansion of coverage and serious efforts at containing costs, it will be a huge achievement even if it falls short of covering every American. But the road there is seeded with land mines, in plain sight but still potentially lethal. Will insurance options include a government-run plan? How will expansion be paid for?

"The devil's in the details, and it's going to get harder as time goes on," the senior official said. And later, in an assessment decidedly devoid of Obama-like lyricism, "The future looks like a big pain in the neck."